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November Bicycles is a brand that’s built their business on selling open mold frames and rims, but that’s about to change.

Shown above is a solid plastic rapid prototype of their new Rail aero rim, the first proprietary design from the company. What makes this interesting is the level of testing done thus far to ensure it’s worth the trouble of producing something new…and what they’ve learned about aerodynamics, watts and real world time and energy savings. The best part is, they’ve put it all out there, making for some great reading.

Of course, aerodynamics are just one part of a rim. The other, particularly for a carbon clincher, is the braking surface and the tech that’s gone into making sure it’s safe and sound. Roll on for the run down…

The rim has a wide, rounded profile, keeping with modern aerodynamics trends. The idea was to make something fast, but at a depth that could be used for all-around riding, too.

Beyond aerodynamics, they wanted something that rode smoothly and comfortably. So, it’s 52mm deep with an 18mm inside width at the tire bead hook at 25mm at the top of the brake track. In their words, they wanted something “optimized for every part of the race course”, which they found in the NACA 0024 profile.

Before we get to the aero testing, which sheds a lot of light on the standards of testing, let’s talk brakes. Here’s what November’s Dave Kirkpatrick told us:

“The first part of the equation is to raise the temperature that the rims can stand before they weaken and fail. Carbon is basically impervious to heat, but the resin isn’t. To a large degree, resin properties have existed on a continuum where resilience and heat tolerance are at odds with one another; high temperature resins have been too brittle for use in wheel applications, but resilient resins have been too heat intolerant. Our rim manufacturer is fortunately high enough up on the food chain that their resin suppliers are paying attention to the issue and addressing it. The new production (which has already gone into effect on the rims we buy from them) uses a resin that is rated to 180°C, or about 360°F. They’ve increased the resilience of the heat tolerant resins. We’ve also given the manufacturer a realistic weight target, allowing them to build the rims with enough meat to withstand life on the road.

“The other side of the equation is the heat that gets generated in the first place. We’ve done a lot of research into brake pads, and there are a lot of good brake pads out there compared to what was available just recently. SwissStop’s new Black Prince pads (Ed: reviewed here) are pretty tremendous at generating less heat. We’re sending some wheels to Switzerland, since SwissStop has a great setup for testing brake pad/rim interaction. That testing will confirm that both the rim and the pad are working hard to make heat much less of an issue than it’s been in the past.”

Kirkpatrick added that the combination of good rims and good brake pads means you can stay off the brakes longer, which means less dragging, which ultimately means less overall heat generation to begin with.

Now for the aerodynamics:

Using their own FSW 23 as a benchmark, they sent all of their wheels plus a pair of Zipp 404 Firecrest (58mm deep) to A2 Windtunnel for testing. This chart shows the time saved over a 40km time trial if you held 30mph, averaged for all AOA (Angle of Attack, or Yaw) wind angles. The Rail prototype tested just two seconds slower than the Zipp wheel, but what makes that pretty remarkable is it’s a shallower wheel and it was built with 24 spokes versus Zipp’s 16. Production Rail wheels will only have 20 spokes, so our hunch is it’ll close that gap a little more when it’s carrying fewer sticks and has a polished carbon finish rather than rough plastic.

Two things worth noting, one plus, one minus. The gap gets even narrower when you bring it down to real world speeds (see chart below), which makes the Rail even more attractive. The unknown and potential negative is rim and total wheel weight…it might be a good bit heavier than the Zipps.

What I found most interesting about November’s test data from A2 was the minimal differences in drag and energy savings when speeds are more like what you and I are riding. At 20mph, the energy savings across most of the wheels is arguably statistically insignificant. At 25mph, it might make a hair of difference.

November Bicycles’ blog has a very detailed analysis of the numbers and more from A2, including a head-to-head test of the same wheel built using Sapim’s Cosmic and CX-Ray spokes to see if bladed spokes really make a difference. Spoiler alert: Like the wheels, speed is the key to getting much advantage out of the more expensive bladed spokes. The story is carried across several blog posts on their site, but reading from the top down (reverse chronological order) won’t ruin it.

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Comments

“Kirkpatrick added that the combination of good rims and good brake pads means you can stay off the brakes longer, which means less dragging, which ultimately means less overall heat generation to begin with.”

Folks with physics degrees, please chime in. I’d say that the overall heat generated has to be the same no matter what rims or pads you use, because what a brake does is convert momentum to heat. Same bike weight, same start speed, same speed reduction = same total heat generated. (Actually bad brakes will have a small advantage, because more time spent braking means more time getting slowed down by air resistance.)

If there is an advantage here, my guess is that with more brake power you spend less time braking, the rim spends less time getting heated, so the heat has less time to transfer throughout the rim where it can do structural damage or blow a tire. The tradeoff is a higher temperature spike in the brake track.

Exactly- all this talk of cool brakes and rims with special coatings to keep things cool is rubbish. Brakes have to get hot to work- converting kinetic energy into heat. If it aint hot it aint stopped! Its managing the heat that matters.

This is why I will continue to love November as a company. They’re really open about what they do. None of that super secret “this is our new technology with a weird-a** name that we claim makes you X% faster” bullsh*t you get from other companies. I’ll gladly take a massive chunk of the performance and save a similarly sized chunk of cash with their products over something from companies like Zipp because of how they run themselves.

Nerio – On their blog, they mention the new Mavic 80mm wheels, but those are too deep for general purpose riding and racing, so they’re comparing to wheels in the same range. Most people aren’t using 80mm deep wheels outside of TT or Triathlon.

On face value Kirkpatrick’s comment about brakes creating less heat is inaccurate or at best an oversimplification. What he might have meant is that it creates less heat problems ? However, longer braking doesn’t make better braking for a number of reasons.

One of the issues regarding dragging your brakes or longer braking periods is that it gives more time to transfer the heat involved in braking into the rim and pad material rather than dissipate it.

In an ideal world the heat from the braking would be immediately vented away from the braking materials and it would continue to operate at whatever ideal temperature for braking is determined by the relative materials. In the real world longer braking periods allow the heat to be transferred to the materials and this causes brake fade, damage to the surfaces and a rolling drop in performance.

Another variable in the system is how the energy gets transferred in the entire system. Powerful brakes cause heat but also flex in the wheel and frame, therefore some of the energy is split away from the direct kinetic/heat equation. Dragging brakes have a more 1 to 1 correlation of transfer.

The two parts he described would be better labeled as making the materials have a higher heat tolerance and better dissipation of the heat generated ?

Loki,
“Another variable in the system is how the energy gets transferred in the entire system. Powerful brakes cause heat but also flex in the wheel and frame, therefore some of the energy is split away from the direct kinetic/heat equation. Dragging brakes have a more 1 to 1 correlation of transfer.”

Braking induced flex stores energy in the flexing bits, but that energy is returned to the system as you release the brakes and they flex back. (I think only a small portion of that energy ends up heating the frame, but I don’t have the numbers.) So the correllation should be very near 1 to 1 in any case.

(To illustrate, imagine a 10 meter wheelbase bike where the frame is super flexy. As you brake the wheelbase is reduced to 2 meters because the front wheel has more traction, but release the brakes and the frame pops out again – so in order to stop at an obstacle you need to stop the bike earlier than with a stiff frame.)

I think you and I are actually in lock step agreement. If it’s not clear from what was attributed to me (I think it was but I have the bias of knowing what I meant), dragging brakes is the worst thing you can do – it continually heats the pad and rim, and causes pad glazing which turns this into a vicious cycle.

The new SwissStop pads do indeed vent better – you can’t miss the vents. But the way I think about it is this – imagine a cast iron Dutch oven and an aluminum stock pot. They play the role of your brake pads. Your hands play the role of your rims. Heat each pot to the same temperature, turn off the flame, and wait two minutes. Grab the handle and lift the cover on each. The iron cover will burn your hand badly, while the aluminum cover will certainly feel warm, but it probably won’t burn you. That’s similar to the dynamic I’m trying to describe – rapid dissipation of heat, so you aren’t imposing a searing hot pad onto the rim with every squeeze of the brakes. Dragging your brakes is equivalent to never turning off the flame, so that’s obviously just plain bad.

And now a chef will weigh in and tell me how much better and more evenly the dutch oven cooks what’s inside,, and how only a philistine would ever compare the two…

It’s a big challenge to write with enough accuracy to satisfy the technically minded yet still be comprehensible to the majority of the audience, especially when you are space compressed. We might sometimes get that balance wrong, but we’ll never intentionally mislead.

Dave, those grooves in the new SwissStop pads aren’t for convective cooling (venting). Those are for clearing debris on the rim (water, dirt). The shape of those grooves isn’t optimized for airflow. In fact, their shape and their position are pretty much what you would want. More importantly, the surface area created by those grooves is very small compared to the surface area of the braking surface, and convective cooling varies directly with surface area.

With respect to the stated values for average time saved and average drag, averages aren’t a good choice for comparing drag. It would be much better to see drag as a function of relative wind angle. Using an average hides the structure of the drag function at different angles. For instance imagine two different drag profiles (as a function of relative wind angle), one is a triangle function (drag linearly increases with angle) and the other is more of an impulse function (drag is constant until it increases instantly to a much higher value at ±?° and stays constant at the new level for the last 5°). Now imagine that both drag functions have the same average drag. Obviously the difference in how that drag varies with angle is completely hidden but wildly different if drag is only represented as an average. Given that, average drag is pretty meaningless, especially now that emphasis is being placed on how rims handle in crosswinds.

The data shown above is actually based on weighted averages, per Tour Magazine’s protocol. The time saved graphic is at 30mph. The watts of drag at different speeds graphic uses a different weighting for each speed (angles widen at slower rider speeds). They aren’t perfect, but they’re very useful – certainly far from meaningless. We’ve spent a ton of time charting apparent wind angles based on various rider speeds and wind speeds, and the huge preponderance of riding time, in competitive situations where wheels such as these would matter, is spent at apparent wind angles of 15 degrees or less. The Tour weighting matched very well with our findings, so in the interest of presenting comprehensible data, we made these graphs. We’ll roll out full spectrum curves for each wheel we tested over the next several days, so you can evaluate them in the conditions you expect to see. Racing crits in the east coast summer would give you a vastly different relevance distribution than riding the Ironman course in Kona, that’s for sure.

Tyler’s done us a huge favor in helping to publicize what we’ve found, but we have posted and will continue to post stacks and stacks of stuff on our site that goes far deeper than what we can do here. For example the blog where the above graphs were first posted has a big discussion of the weighting.

Crosswinds handling is a funny one. I’ve yet to really wrap my head around how to accurately quantify that, and I don’t think the stall break severity is an accurate analog of it – otherwise people riding on some of the fastest deep wheels would be getting thrown sideways whenever their AoA went from 17* to 18*. If the drag vs AoA chart explained it, a HED H3 would be the ultimate crosswind wheel – it’s pretty much a flat line from 0 to 20*. I’ve explained it as well as I can from my significant sailing and sail design background on the blog. Plainly stated, rounder entries are going to give more predictable handling.

The grooves are, as you state, optimized for water and debris clearance, but there is definitely a lot more exposed surface area, and I don’t want to reveal things that aren’t mine to reveal. In any case, SwissStop has tested the Black Prince as developing 170c max heat in a 60kmh to 0 full stop test, compared to 303c max heat with a Yellow King. Distance to stop from 60kmh in wet conditions was reduced from 120m with Yellow Kings to 90m with Black Prince in SwissStop’s testing. Their protocol and testing infrastructure is a lot more elegant than what we’ve used (big reason why we’re having them do our formal testing) but based on our testing, their pads stop better with less heat issues.

This is the ultimate David vs. Goliath story. They have nice technical justifications for their design features on their blog, but it sounds almost too good to be true. 95+% of the aerodynamics of a 404 achieved with a shallower rim depth and an 18 mm wide inside width, too, to achieve that “tubular-like ride quality”.

From what I could see on their website, though, this company has mostly dealt with open-mold components. So after consulting, tool design and cost, resin and layup research and testing, or whatever else they have to do to bring this concept to life, its hard to imagine that they will be able to offer these rims at a price even close to that of their current line-up. If they could, though, it would be the golden bullet. This story will be interesting to follow and Im definitely rooting for them!

I love that they bring some reality to their aero data. They don’t compare their rims to the “OE Rim”, usually a Mavic Open Pro box section. Really, when is the last time you saw an Open Pro as the spec on anything other than a custom bike? And they give us a range of speeds. If you can push the 30mph of most aero tests, then you are likely getting your wheels for free. Finally, they give the data in watts instead of grams of drag, to save us the trouble of dividing by 10 (yes, I know it is a slightly different divisor at different speeds), but more importantly, present the data in the scale that is meaningful to their audience.

This honest approach goes a long way towards building trust in a new brand that is going to have to fight hard in a crowded market.

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